(1) Field of the Invention
The present invention relates to a valve for opening and closing a fluid conduit. More specifically, the present invention relates to an apparatus for opening and closing a gas pipe having a generally wide cross section. Although not limited thereto, the invention has utility in a pipe for conducting crude blast furnace gases from a blast furnace used in the manufacture of steel.
(2) Description of the Prior Art
In the manufacture of steel, crude gas at the top of the blast furnace is directed vertically through a collector pipe. The collector pipe directs the gas to a purifying installation such as a dust removal means wherein particulate matter is separated from gases. The crude gas from a blast furnace comprises a mixture of combustion gases, steam and particles of dust having varying sizes. The crude gas is released from the blast furnace at high temperatures and high pressures. Because the gas is under high pressure and temperature and contains particulate matter, the mechanical elements which contact the crude gas such as sealing surfaces and the like are vulnerable to considerable wear and strain.
In a collector pipe, it is particularly important to provide a valve for opening and closing the pipe in order to isolate the source of the crude gas, that is, the blast furnace and other mechanical devices situated downstream of the source of the crude gas. It is desirable that the mechanical means of opening and closing the collector pipe be capable of being rapidly actuated and have a relatively simple structure. Conventional collector pipes are equipped with an apparatus for stopping up the pipes in order to allow isolation of the blast furnace. A conventional collector pipe has a generally cylindrical shape and includes a slit transverse to the axis of the pipe. The slit defines a plane through which a variety of planar plates are moved in and out of the slit to open and close the collector pipe. A valve of this type is described in German Pat. No. 2,136,216. The most common valves comprise a planar disc or cover which is slid perpendicular to the axis of the pipe into the pipe. Another type of valve is a "goggle valve" which comprises a plate having a circular opening at one end and being solid at the other end. With this type of plate, when the opening is aligned with the collector pipe, the collector pipe is in open condition. When the solid part of the plate is aligned in the collector pipe, the collector pipe is in the closed position.
The valves for opening and closing the collector pipe must satisfy accident prevention standards which require that no person may work downstream of the blast furnace except behind a fully closed collector pipe. That is, the pipe must be completely closed in the direction transverse to the axis of the pipe so that the risk of crude gas being allowed to pass downstream of the valve is practically nil. In the case of collector pipes under high temperatures and pressures, the conventional valves fail to provide sufficient hermetic sealing from the inside of the collector pipe to the outside of the collector pipe. Also, during opening and closing of the valve, there is considerable leakage of the crude gas to areas external to the pipe. To prevent leakage of crude gases, the valve is provided with a tight armoring that completely surrounds the valve and the mechanism which moves the valve in order to insure hermetic sealing. Because the plate of the valve is moved inwardly and outwardly of the collector pipe in a plane transverse to the axis of the pipe, the armoring of the valve must extend a generally large distance away from the outer wall of the collector pipe. An armoring which is capable of withstanding the large pressures and temperatures associated with crude gas from a modern blast furnace must have increased weight in order to provide sufficient sealing. Moreover, in order to allow access to the valve for repair or replacement, an expensive and cumbersome superstructure for supporting the valve and the armoring must be provided. In modern blast furnaces, the tendency to operate at increasingly high pressures aggravates the foregoing problems.
Because of the very nature of crude gas from a blast furnace, particularly its high humidity and particulate content, the sealing surfaces of the valve and the control elements for operating the valve are subject to wear and, thus, the valve parts must be repaired or replaced periodically. Moreover, the particulate matter from the crude gas deposits on the plate of the valve when the plate is introduced into the pipe. Since the plate is planar and is displaceable transversely with respect to the axis of the pipe, a comparatively large planar surface is exposed. The removal of deposits from this surface is difficult.
The purpose of the present invention is to provide a valve for opening and closing a conduit having a wide cross section. One object of the present invention is to provide improved hermetic sealing of the valve with respect to the environment external to the conduit.
Another object of the present invention is to reduce the weight of the equipment required to support the valve and its armoring. It is another object of the invention to reduce the weight of the superstructure required to support the valve and its armoring. It is still a further object of the present invention to provide a valve and armoring which may be fitted into a smaller space.
It is still a further object of the present invention to provide a valve and armoring which facilitates maintenance and cleaning of the valve.